Mixed Pharmceuticals Adsorption, Oxidation and Catalytic Chlorination by Metal Oxides

With the advance of medicine, more and more synthetic drugs have been invented and used. These chemicals will enter the environment because of human excretion and improper disposal. The waste water treatment plant cannot remove the pollution completely, and our environments will be contaminated by these chemicals. Although their concentrations in the wastewater systems and environments usually range from ng/L to g/L level, many studies show that exposure to pharmaceutical substances can result in adverse effects to aqueous species. Chlorination procedure is the most commonly applied disinfection methods for water and wastewater treatments due to its low cost. Chlorine gas hydrolyzes in water to form hypochlorous acid (HOCl), while HOCl is a weak acid which dissociates in aqueous solutions. Chlorine is a strong oxidant that reacts with the organic matter in water; especially reacts with organic compounds containing aromatic system, neutral amines and double bonds. Many researches have been done about the removal characteristics of single pharmaceutical compound by chlorine. However, multiple pharmaceuticals may be present in wastewater or in environments. In this study, we selected three different pharmaceuticals, Acetaminophen, Sulfamethoxazole and Diclofenac, which are frequently used and be often detected in wastewater and surface water to investigate their transformation by chlorination. The effects of dose of chlorine and pH value were also investigated. The results indicate that pH value significantly influenced the transformation of all the three pharmaceuticals. The transformation of Sulfamethoxazole and Diclofenac in acidic condition was faster than that in neutral or alkali conditions, while the transformation of Acetaminophen in alkali condition was more effective. Similar results have been observed in previous studies. UPLC-Q-TOF MS were used to identify transformation products. In single pharmaceutical system, we find two products of Acetaminophen, 7 products of Sulfamethoxazole and 6 products of Diclofenac. Some of these products were also found in previous study, but few of them are new. In multiple pharmaceuticals system, we find two products which were not found in single pharmaceutical system. These products may be polymers of the transformation products and pharmaceuticals. Therefore, chlorination of multiple pharmaceuticals may form more products and be more complicated than that of signal pharmaceutical.